High school student and girls' tennis club leader Ayu Tateishi bumps into transfer student Nina Sakura, who is crying apparently because she has lost something. Later on, Ayu finds a pink electronic device and gives it to Nina. As a reward for finding her item, Nina reveals to Ayu that she is a witch in training and she offers to cast her a spell to help her win in a tennis game against the boys' club. Unfortunately, the spell doesn't enhance Ayu's abilities; instead, it turns her into a boy.